The present invention relates generally to printing devices and more particularly to a web infeed device for rotary printing devices.
U.S. Pat. No. 5,967,036 describes a web infeed device for rotary printing presses, which permits a web to be fed through the printing press. A flexible, finite infeed element for holding a lead edge of a web runs in a guide or track. Balls are inserted in openings of the infeed element at spaced-intervals, and travel within a cross-cut in the guide. Drive elements can drive the balls and thus move the infeed element through the printing press to feed the web. U.S. Pat. No. 5,967,036 is hereby incorporated by reference herein. It has been known for the tip of the infeed element described therein to jam in the guide, for example in curves or gaps.
U.S. Pat. No. 5,320,039 discloses a web engagement system for an off-reel printing press in which a guide piece is accommodated in a guide channel. The guide piece preferably is a flexible plastic section with a square cross-section. The front part is tapered and a rear part is split.
U.S. Pat. No. 4,987,830 discloses a paper feed device for rotary presses having a spindle shaped linear member. The linear member is made of synthetic resin or leather, with caps being made of a rather hard material.
The devices of the '039 and '830 are long flexible members that ran in guides and contact the guides over a large length. The friction generated by flexible members passing over a curved section is subject to what is known as the capstan effect, which causes frictional forces to increase exponentially as the flexible member wraps around the surface.